1. Field of the Invention
The present invention relates to the structure of an ink cartridge used in an inkjet recording apparatus and to an inkjet recording apparatus using this ink cartridge.
2. Description of the Related Art
In recent years, inkjet recording apparatuses (inkjet printers) have become widely used as apparatuses which print and record images that have been captured by a digital camera, and the like. Many domestic inkjet recording apparatuses use a serial scanning system which ejects ink while scanning (moving) a print head mounted on a carriage back and forth reciprocally in the main scanning direction, which is perpendicular to the paper conveyance direction. In such domestic inkjet recording apparatuses, vertically disposed ink cartridges (ink tanks) are arranged in the upper portion of the print head.
An ink absorbing body, such as a polymer foam body, is disposed inside a conventional ink cartridge of this kind, and a negative pressure is generated by means of the capillary force of the ink absorbing body. Japanese Patent Application Publication No. 6-155759 discloses a structure in which a pressure adjuster for generating negative pressure using a spring is disposed inside a cartridge, in view of the environmental problems which arises with the disposal of polymer foam bodies inside used cartridges. However, Japanese Patent Application Publication No. 6-155759 does not disclose a method for determining the remaining amount of ink. In view of this point, Japanese Patent Application Publication No. 2002-248795 discloses a composition in which the remaining amount of ink is determined by means of a sensor which determines the position of a lever which abuts against an ink bag having an external diameter dimension that varies in accordance with the ink volume.
As described above, in the structure commonly employed in domestic inkjet recording apparatuses, in other words, in a system in which an ink cartridge is mounted on a head on a carriage, since a cartridge having a large volume is carried on the upper portion of the head and is moved back and forth reciprocally (in a main scanning action) together with the head, it is necessary to provide a large space inside the apparatus to allow for the travel of the head, and hence there is a problem in that space is not used efficiently.
Furthermore, since the conventional ink cartridge described above accommodates a member such as a polymer foamed body, as well as ink, inside the cartridge, then there is a problem in that the ink accommodation efficiency is poor.
On the other hand, in wide format printers, such as commercial printers, an ink bag system which has good ink accommodation efficiency is known, but since a negative pressure is applied in accordance with the lifting height, then there are restrictions on the position in which the ink bag can be disposed if it is sought to set the internal pressure of the head to a specific pressure.
Furthermore, when using an ink bag system, it is difficult to ascertain accurately the amount of change in the volume of the bag, and therefore in the conventional remaining amount of ink determination method disclosed in Japanese Patent Application Publication No. 2002-248795, it is difficult to ascertain the remaining amount of ink accurately. In particular, when using an ink bag system in an ink cartridge having a relatively small volume, such as a domestic inkjet recording apparatus, it is even more difficult to determine the volume change accurately. Consequently, it is not possible to use up the ink inside the ink bag accurately, right up to the last, and hence there is a possibility that the amount of wasted ink is large.